1. Field of the Invention
The present invention relates to a process for the physical and/or biological purification of sewage by means of a filter-biofilter, wherein mechanically prepurified sewage is distributed evenly over an artificially aerated filler material and is trickled through the latter. The trickling is continued for a limited time until the sewage has coated the surfaces of the filler material more and more with sludge and microorganisms whereby the passage of air through the filler has been decreased more and more because of the incrustation of the interstices of the filler material. Then the largest part of the excess sludge is withdrawn from the filler material by turning it over and subsequently the time-limited and repeated trickling of the sewage through the filler material is reinstituted again. An abrasion resistant filler material is used and for the purpose of turning over of the filler material the filter-biofilter is filled up with water, then the dammed up water and filler material is turned over within the filter-biofilter by blowing in of compressed air. At the same time the mineral or biological sludge, filler material and dammed up rinsing water are drawn off from the mixture of these items that is developing and afterwards the rinsing water is discharged.
2. Description of the Prior Art
Such a process has become known through the German published application Nos. 2,116,000 and 2,150,345. This known process is carried out in such a way, that both the turning-over and rinsing as well as the drawing off of sludge is accomplished only at certain places in the filter-biofilter, as a result of which a sufficient sludge removal from the filler material is achieved with relatively small biofilters, that is to say, biofilters having a diameter up to about 10 M, while in the case of larger biofilters with a diameter of for example about 20 M, only an incomplete sludge removal takes place, since in the available areas, which are not encompassed by the turn-over of the removal of sludge, pockets remain between the places at which both the turning over and rinsing, as well as the removal of sludge takes place. In the case of purification with clear water, such areas are not encompassed by the turning-over and rinsing would be without any harmful effect on the purified clear water because of the purely mechanically accomplished purification and because of the bacteria-free minerals used thereby. In the case of biological purification of sewage constituting the starting point of the invention however, a digestion occurs in the areas not encompassed by the turning-over and the rinsing in the sludge pockets, which on the one hand deteriorates the flow off from the filter-biofilter to an unadjustable extent and which on the other hand causes a quick resludging of the filler material, as a result of which the purifying effect of the filter-biofilter is substantially decreased.
This is where the present invention starts, which is based on the task of creating a process for the physical and/or biological purification of sewage by means of a filter-biofilter, in which the filler material is desludged effectively in all its areas. For the solution of this task the proposal is made according to the invention, that the turning-over and removal of sludge is accomplished continuously in a horizontal direction right through the contents of the filter-biofilter. Effectively the progressive turning-over and removal of sludge is carried out continuously.
It has now been achieved that because of the continuously carried out turning-over and rinsing, all areas in the filler material are encompassed successively and as a result of which are desludged effectively. This process makes it possible that now the above mentioned large biofilters, as can be used in the case of large quantities of sewage obtained from several tens of thousands of inhabitants, can be highly loaded without the purification effect being impeded and without there being any necessity for a much too frequent desludging of the filler material. Basically the invention can also be used in the form of a filter-biofilters developed as a longitudinal basin.
Insofar, however, as the filter-biofilter is developed in a known manner in the form of an upright cylinder, the proposal is made according to the invention, that the progressive turning-over and desludging is accomplished in the sense of a rotational movement taking place around the center of the biofilter. The locally fixed desludging grates provided for the desluding of the biofilter in the filter-biofilters known by way of the above mentioned German published application Nos. 2,116,000 and 2,150,345, the annular sludge removal pipes and the slanted sludge removal metal sheets, as well as the likewise locally fixed perforated rooflike superstructures and aerating pipes serving for the turning-over by means of compressed air and cooperating therewith, are to be sure sufficient in their effect for relatively small quantities of sewage. In the case of large quantities of sewage, as obtained from several tens of thousands of inhabitants, and which are to be purified with the aid of the above mentioned relatively large filter-biofilters, the desludging in the case of known filter-biofilters must however be carried out relatively often and each time over relatively large periods of time, since the turning-over and desludging effect is too insignificant and since pockets of sludge develop in the areas between the above mentioned desludging and turning-over arrangements, so that in this case the known filter-biofilters are unsuitable. Therefore a filter-biofilter for the carrying out of the proposed process is to be created by the invention, which can be produced in a sufficient size and while avoiding high expenditure and which desludges effectively and in a simple manner.